Heat a dry frying pan over a medium-low heat until you can feel the heat rising. Apart from the turmeric, add all the other spices and the chana dal and roast for a minute, shaking the pan from time to time until you can smell the aroma of the spices. Watch carefully so they do not burn. Remove the pan from the heat and immediately tip the spices on to a plate and leave to cool completely.

Transfer the spices along with the turmeric to a spice mill and blend until finely ground. Store the mixture in an airtight container, away from direct sunlight, for up to 6 months.